In visiting farms across the state this year to evaluate projects and here at the research center, I have noticed some symptoms that couldn't quite be explained by our known soybean diseases.
Figure 1. Symptoms of an unknown soybean disease (PSU photo).
These symptoms can resemble scald or Cercospora leaf blight, but they are centered around the veins, and as they progress they move out from the veins in a “front of discoloration” (Figure 1).
We believe that these are the symptoms of a relatively new virus called Soybean Vein Necrosis Virus (SVNV). This was discovered in 2008 in Tennesee and Arkansas and has since been confirmed in New York and most recently in Delaware and Maryland.
This virus is in the group referred to as the tospoviruses. Other members of this group include Tomato Spotted Wilt Virus and Inpatiens Necrotic Spot Virus. These are viruses that are vectored (moved from plant to plant) by thrips. This means there is the potential to manage this disease by managing the vector.
Another potential option for management of this disease will be genetic resistance in soybean lines. We do not yet know whether or not this is a yield-impacting disease.
The level of leaf damage I have seen in the state suggests that at least this year we will not see yield reduction from this virus. In some cases, plants that are infected by multiple viruses may have a significantly reduced yield.
We have seen some outbreaks of bean pod mottle virus this year, and if the two occur in the same plant, it may overwhelm the plant’s resources.
I've been in contact with Dr. Ioannis Tzanetakis at University of Arkansas and will be sending samples to confirm the virus in Pennsylvania. Stay tuned to Field Crop News to learn of any updates.